Organopolysiloxanes and the use thereof in substances that can be cross-linked at room temperature

ABSTRACT

The invention relates to organopolysiloxanes containing at least one unit of formula (I) R 2 SiO 2/2 , at least one unit of formula (II) (R 5 O)R 2 SiO 1/2 , and at least one unit of formula (III) (R 1 R 2 N—CR 10   2 —)RSiO 2/2 , whereby the radicals and indices have the meanings as cited in Claim  1.  The invention also relates to the production of these organopolysiloxanes and to their use in substances that can be cross-linked at room temperature, particularly in those that cross-link while alcohols are separated.

The invention relates to organopolysiloxanes having nitrogen-containingradicals, to the preparation thereof and to the use thereof in roomtemperature crosslinkable compositions, especially those which crosslinkwith elimination of alcohols.

Siloxane-based polymers for RTC compositions are common knowledge, suchas alkoxysilylalkylene-terminal polymers (see, for example, U.S. Pat.No. 6,037,434) or alkoxysilyl-terminal polymers (see, for example, EP-A1 006 146). For economic and technical reasons, only a limited range ofpolymer viscosities is available for the production of RTC rubbers. Forlow-modulus sealants, however, more highly viscous polymers are requiredand should preferably be generated from standard polymers in the courseof the preparation of RTC compositions.

To increase the viscosity of the polysiloxanes and thus reduce thetension of RTC rubbers produced therefrom, longer polymers can beprepared from shorter polymers by chain extension. It is known that itis possible for this purpose to use difunctional silanes or siloxaneswhich are thought to have a sufficiently high reactivity. For instance,U.S. Pat. No. 5,110,967 describes Si—N heterocyclic silanes, but theseneed specific crosslinkers to be used in the formulation of RTCcompositions. Compounds such as bisacetamidosilanes (see, for example,U.S. Pat. No. 5,290,826), bisacetoxysilanes (see, for example, U.S. Pat.No. 842,586) or bisaminosilanes (see, for example, EP-A 74 001) releasecleavage products in the course of vulcanization which are dangerous tohealth or corrosive. Bisacetoxysilanes additionally require the additionof aminic compounds (see, for example, U.S. Pat. No. 842,586).Preference is therefore very frequently given to alcohol as a cleavageproduct, for which the dialkoxysilanes or -siloxanes described in U.S.Pat. No. 5,300,612 and U.S. Pat. No. 5,470,934 are generally unsuitablefor a rapid reaction with silanol-terminal siloxanes. Whenaminomethyldialkoxymethylsilanes are used, a rapid reaction does takeplace with polysiloxanes, but the resulting polymer is also decomposedagain when it is used in RTC compositions in the presence of activehydrogen-containing substances, such as alcohol, which are alwayspresent. RTC compositions damaged in this way usually no longervulcanize.

The invention provides organopolysiloxanes containing at least one unitof the formulaR₂SiO_(2/2)  (I)at least one unit of the formula(R⁵O) R₂SiO_(1/2)  (II)and at least one unit of the formula(R¹R²N—CR¹⁰ ₂—)RSiO_(2/2)  (III)where

-   -   R may be the same or different and is a monovalent, optionally        substituted hydrocarbon radical,    -   R′, R³, R⁴, R⁷, R⁸ and R⁹ may each independently be the same or        different and be as defined for R,    -   R¹ and R¹⁰ may each independently be the same or different and        be hydrogen or be as defined for R,    -   R² is a —C(═O)—NH—R³ radical or a —C(═O)(OR⁴) radical,    -   R⁵ may be the same or different and be a hydrogen or a        —(R′₂Si—R⁶—)_(y)Si(OX)_(a)R⁷ _(3−a) radical,    -   X is —C(═O)—R⁸, —N═CR⁹ ₂ or is as defined for the R radical,    -   R⁶ may be the same or different and is a divalent, optionally        substituted hydrocarbon radical,    -   a is 1, 2 or 3 and    -   y is 0 or 1.

In the context of the present invention, the term organopolysiloxanesshall embrace polymeric, oligomeric and dimeric siloxanes, in which someof the silicon atoms may also be joined to one another by groups otherthan oxygen, such as via —N— or —C—.

The inventive organopolysiloxanes are preferably those of the formula(IV)

where

-   -   R, R¹, R² and R⁵ are each as defined above,    -   o is ≧1,    -   m is ≧1 and    -   n is ≧1,        with the proviso that the individual units may be distributed in        any manner within the molecule.

The values of m, n and o are selected such that the viscosity of theinventive organopolysiloxanes of the formula (IV) is preferably between5000 and 1 000 000 mPa·s, more preferably between 20 000 and 500 000mPa·s, in particular between 50 000 and 200 000 mPa·s, based in eachcase on 20° C.

The inventive organopolysiloxanes are more preferably those of theformula (I) having an n:o ratio of preferably ≧1, more preferably ≧50,in particular ≧100.

The R, R′, R³, R⁴, R⁷, R⁸ and R⁹ radicals are preferably eachindependently monovalent hydrocarbon radicals optionally substituted byheteroatoms such as nitrogen atoms, halogen atoms and oxygen atoms, andhaving from 1 to 12 carbon atoms.

Examples of R, R′, R³, R⁴, R⁷, R⁸ and R⁹ radicals are alkyl radicalssuch as the methyl, ethyl, n-propyl, isopropyl, 1-n-butyl, 2-n-butyl,isobutyl, tert-butyl, n-pentyl, isopentyl, neopentyl, tert-pentylradical, hexyl radicals such as the n-hexyl radical, heptyl radicalssuch as the n-heptyl radical, octyl radicals such as the n-octyl radicaland isooctyl radicals such as the 2,2,4-trimethylpentyl radical, nonylradicals such as the n-nonyl radical, decyl radicals such as the n-decylradical, and dodecyl radicals such as the n-dodecyl radical; cycloalkylradicals such as cyclopentyl, cyclohexyl, cycloheptyl andmethylcyclohexyl radicals; alkenyl radicals such as the vinyl,5-hexenyl, cyclohexenyl, 1-propenyl, allyl, 3-butenyl and 4-pentenylradical; alkynyl radicals such as the ethynyl, propargyl and 1-propynylradical; aryl radicals such as the phenyl radical; alkaryl radicals suchas o-, m-, p-tolyl radicals; and aralkyl radicals such as the benzylradical, the α- and the β-phenyl-ethyl radical.

Examples of substituted R, R′, R³, R⁴, R⁷, R⁸ and R⁹ radicals arehaloalkyl radicals such as 3,3,3-trifluoro-n-propyl radical, the2,2,2,2′,2′,2′-hexafluoroisopropyl radical, the heptafluoroisopropylradical and haloaryl radicals such as the o-, m- and p-chlorophenylradical, and also all radicals mentioned above for R, R′, R³, R⁴, R⁷, R⁸and R⁹ which may be substituted by mercapto groups, epoxy-functionalgroups, carboxyl groups, keto groups, enamine groups, amino groups,aminoethylamino groups, isocyanato groups, aryloxy groups, acryloyloxygroups, methacryloyloxy groups, hydroxyl groups and halogen groups.

The R radical is more preferably an alkyl radical having from 1 to 6carbon atoms, in particular the methyl radical.

The R′ radical is more preferably an alkyl radical having from 1 to 6carbon atoms, in particular the methyl radical.

The R³ radical is more preferably an alkyl or aryl radical optionallysubstituted by divalent radicals of the formula —NH—C(═O)—, inparticular alkyl radicals having from 1 to 12 carbon atoms.

The R⁴ radical is more preferably an alkyl radical having from 1 to 6carbon atoms, in particular the methyl and the ethyl radical.

The R⁷ radical is more preferably an alkyl radical having from 1 to 6carbon atoms, in particular the methyl radical.

The R⁸ radical is more preferably an alkyl radical having from 1 to 6carbon atoms, in particular the methyl radical.

The R⁹ radical is more preferably an alkyl radical having from 1 to 6carbon atoms, in particular the methyl or ethyl radical.

The R¹⁰ radical is more preferably a hydrogen atom.

The R¹ radical is preferably a radical specified above for R, morepreferably alkyl or aralkyl radicals having from 1 to 12 carbon atoms,in particular the cyclohexyl, methyl or ethyl radical.

The R² is preferably the —C(═O)—NH—R³ radical where R³ is as definedabove, more preferably an alkyl radical having from 1 to 6 carbon atoms.

The R⁶ radical is preferably a divalent hydrocarbon radical optionallysubstituted by heteroatoms such as a nitrogen atom, halogen atom andoxygen atom, and having from 1 to 12 carbon atoms.

Examples of divalent R⁶ radicals are alkylene radicals such as themethylene, ethylene, n-propylene, isopropylene, n-butylene, isobutylene,tert-butylene, n-pentylene, isopentylene, neopentylene, tert-pentyleneradical, hexylene radicals such as the n-hexylene radical, heptyleneradicals such as n-heptylene radical, octylene radicals such as then-octylene radical and isooctylene radicals such as the2,2,4-trimethylpentylene radical, nonylene radicals such as then-nonylene radical, decylene radicals such as the n-decylene radical,dodecylene radicals such as the n-dodecylene radical; alkenyleneradicals such as the vinylene and the allylene radical; cycloalkyleneradicals such as cyclopentylene, cyclohexylene, cycloheptylene radicalsand methylcyclohexylene radicals; arylene radicals such as the phenyleneand the naphthylene radical; alkarylene radicals such as o-, m-,p-tolylene radicals, xylylene radicals and ethylphenylene radicals;aralkylene radicals such as the benzylene radical, the α- and theβ-phenylethylene radical.

The R⁶ radical is more preferably an ethylene or propylene radical, inparticular the ethylene radical.

y is preferably 0.

a is preferably 2.

X is preferably as defined for the R radical or —N═CR⁹ ₂, particularpreference being given to the methyl radical.

The R⁵ radical is more preferably an alkoxysilyl group or hydrogen atom,in particular an alkoxysilyl radical.

Examples of the inventive organopolysiloxanes areHO—(Me₂SiO)₅₀₀—SiMe[CH₂—NCy-(C=O)NHCy]—(OSiMe₂)₅₀₀—OH,(MeO)₂MeSi—O—(Me₂SiO)₆₅₀—SiMe[CH₂NCy-(C═O)NHCy]—(OSiMe₂)₆₅₀—O—SiMe(OMe)₂,HO—(Me₂SiO)₅₀₀—{SiMe[CH₂—NCy-(C═O)NHCy]—(OSiMe₂)₅₀₀—O}₃H and(MeO)₂MeSi—O—(Me₂SiO)₁₀₀₀—{SiMe[CH₂—NCy-(C═O)NHCy]—(OSiMe₂)₁₀₀₀—O}₂—SiMe(OMe)₂,where Cy is a cyclohexyl and Me is a methyl radical.

The inventive organopolysiloxanes have the advantage that they have ahigh stability with respect to degradation during storage.

In addition, the inventive organopolysiloxanes have the advantage thatthey can be used universally in condensation-crosslinking compositions,without polymer degradation and thus disruptions to vulcanizationoccurring.

The inventive organopolysiloxanes may be prepared by any processes knownin organosilicon chemistry.

In a preferred procedure, in a

-   -   first step, hydroxy-terminated organopolysiloxanes are reacted        with silanes of the formula        R¹HN—CH₂—SiR(OR¹¹)₂  (V)        and/or partial hydrolyzates thereof, where R and R¹ are each as        defined above and R¹¹ may be the same or different and be as        defined for R, and, in a    -   second step, the amino groups of the reaction product obtained        in the first stage are converted to urea groups or carbamate        groups using compounds selected from isocyanates, reactive        isocyanate derivatives and reactive carboxylic acid derivatives,        for example carboxylic anhydrides or carbonyl chlorides.

If further branching of the inventive organopolysiloxanes is desired, itis possible in the second step of the process according to theinvention, for example, also to use oligofunctional isocyanates, so thata plurality of siloxane polymers, for example of the type of the formula(I), can be bonded via the R³ radical.

In a particularly preferred procedure, in a

-   -   first step, hydroxy-terminated organopolysiloxanes are reacted        with silanes of the formula        R¹HN—CH₂—SiR(OR¹¹)₂  (V)        and/or partial hydrolyzates thereof, where R and R¹ are each as        defined above and R¹¹ may be the same or different and be as        defined for R, and, in a    -   second step, the amino groups of the reaction product obtained        in the first stage are converted to urea groups using        isocyanates.

If desired, the organopolysiloxanes prepared in accordance with theinvention may subsequently be end-capped in a third step withorganosilicon compounds, for example silanes of the formulaSi(OX)_(a′)R⁷ _(4−a′) (VI), by customary methods which are known tothose skilled in the art of siloxane chemistry, where X and R⁷ are eachas defined above and a′ is 2, 3 or 4.

The present invention further provides a process for preparing theinventive organopolysiloxanes, characterized in that,

-   -   in a first step, hydroxy-terminated organopolysiloxanes are        reacted with silanes of the formula        R¹HN—CH₂—SiR(OR¹¹)₂  (V)        and/or partial hydrolyzates thereof, where R and R¹ are each as        defined above and R¹¹ may be the same or different and be as        defined for R,    -   in a second step, the amino groups of the reaction product        obtained in the first stage are converted to urea groups or        carbamate groups using compounds selected from isocyanates,        reactive isocyanate derivatives and reactive carboxylic acid        derivatives, and,    -   optionally in a third step, the organopolysiloxanes obtained in        the second step are end-capped with silanes of the formula        Si(OX)_(a′)R⁷ _(4−a′) (VI) where X and R⁷ are each as defined        above and a′ is 2, 3 or 4.

Examples of the silanes of the formula (V) used in the process accordingto the invention are CyHN—CH₂—Si(CH₃)(OCH₂CH₃)₂,C₆H₅—CH₂—HN—CH₂—Si(CH₃)(OCH₃)₂ and (H₃C—CH₂)HN—CH₂—Si(CH₃)(OCH₂CH₃)₂,where Cy is the cyclohexyl radical.

In the first step of the process according to the invention, silanes ofthe formula (V) are used in amounts such that the molar Si—OH/OR¹¹ ratiois preferably greater than or equal to 1.

Examples of isocyanates which can be used in the second step of theprocess according to the invention are cyclohexyl isocyanate, isophoronediisocyanate or hexamethylene diisocyanate.

Examples of reactive isocyanate derivatives which can be used in thesecond step of the process according to the invention are the reactionproducts of the abovementioned isocyanates with phenol or caprolactam.

Examples of carboxylic acid derivatives which can be used in the secondstep of the process according to the invention are acetic anhydride andacetyl chloride.

If isocyanates are used in the second step of the process according tothe invention, they are preferably used in molar amounts of from 100 to120%, based on the silanes of the formula (V) used.

If carboxylic acid derivatives are used in the second step of theprocess according to the invention, they are preferably used in molaramounts of 100-130%, based on the silanes of the formula (V) used.

If the third step of the process according to the invention is carriedout, silanes of the formula (VI) are used preferably in amounts of from1 to 5 parts by weight, based on 100 parts by weight of thehydroxy-terminated polysiloxane used.

The components used in the process according to the invention may eachbe one type of such a component or else a mixture of at least two typesof a particular component.

The process according to the invention is carried out at temperatures ofpreferably from 5 to 100° C., more preferably at room temperature, i.e.about 20° C., and a pressure of the surrounding atmosphere, i.e. fromabout 900 to 1100 hPa.

The individual steps of the process according to the invention may becarried out separately or as what is known as a one-pot reaction in onereaction vessel.

During the inventive reaction, R¹¹—OH is formed and may remain in thereaction mixture or be removed by known methods, where R¹¹ is as definedabove.

Overall, the result is thus a production process which includesexclusively fast reactions, so that the process according to theinvention may be carried out either continuously or batchwise.

The process according to the invention has the advantage that it israpid and simple to carry out, and readily available raw materials areused as reactants.

A particular advantage of the process according to the invention is thatit can be conducted as a one-pot reaction (or gradual reaction in thecase of continuous production), since no deactivation whatsoever of anyadditives or a workup of the organopolysiloxane prepared after one ofthe substeps is necessary.

A further advantage of the process according to the invention is thatthe organopolysiloxanes prepared may be used further directly, forexample in the preparation of RTC compositions.

The inventive organopolysiloxanes or those which are prepared inaccordance with the invention may be used for all purposes for whichorganopolysiloxanes have also been used hitherto. In particular, aresuitable for the preparation of room temperature crosslinkablecompositions.

The present invention further provides compositions crosslinkable bycondensation reaction, characterized in that they comprise inventiveorganopolysiloxanes or those which are prepared in accordance with theinvention.

In addition to the inventive organopolysiloxanes, the inventivecompositions comprise all components which have also been used hithertofor the preparation of room temperature crosslinkable organopolysiloxanecompositions, known as RTC compositions. The hydrolyzable groups whichthe organosilicon compounds involved in the crosslinking reaction mayhave may be any groups such as acetoxy, oximato and organyloxy groups,such as ethoxy radicals, alkoxyethoxy radicals and methoxy radicals, thecompositions preferably being single-component compositionscrosslinkable at room temperature by means of organyloxy groups.

Examples of components which can be used in the preparation of theinventive RTC compositions are condensation catalysts, reinforcingfillers, nonrein-forcing fillers, pigments, soluble dyes, odorants,plasticizers such as room temperature liquid dimethylpolysiloxanesend-capped by trimethylsiloxy groups or phosphoric esters, fungicides,resinous organopolysiloxanes, including those composed of(CH₃)₃SiO_(1/2) and SiO_(4/2) units, purely organic resins such as homo-or copolymers of acrylonitrile, of styrene, of vinyl chloride or ofpropylene, in which case such purely organic resins, in particularcopolymers of styrene and n-butyl acrylate, may have been generated byfree-radical polymerization of the monomers mentioned actually in thepresence of diorganopolysiloxane having in each case one Si-bondedhydroxyl group in the terminal units, corrosion inhibitors, polyglycolswhich may be esterified and/or etherified, oxidation inhibitors, heatstabilizers, solvents, agents for influencing the electrical propertiessuch as conductive black, flame retardants, light stabilizers and agentsfor prolonging the skin formation time, such as silanes havingSiC-bonded mercaptoalkyl radicals, and also cell-generating agents forexample azodicarbonamide. It is equally possible to add adhesionpromoters, preferably aminoalkyl-functional silanes such asγ-aminopropyltriethoxysilane.

To prepare the inventive compositions, preference is given to usingcondensation catalysts. The condensation catalysts may be any which havealso been present hitherto in compositions which are storable with theexclusion of water and crosslink at room temperature on ingress of waterto give elastomers.

Examples of such condensation catalysts are organic compounds of tin,zinc, zirconium, titanium and aluminum. Preference is given among thesecondensation catalysts to butyl titanates and organic tin compounds suchas di-n-butyltin diacetate, di-n-butyltin dilaurate, and reactionproducts of silane having, as hydrolyzable groups, at least twomonovalent hydrocarbon radicals per molecule which are bonded to siliconvia oxygen and optionally substituted by an alkoxy group, or oligomerthereof, with diorganotin diacylate, all valencies of the tin atoms inthese reaction products being saturated by oxygen atoms of the ≡SiOSn≡moiety or by SnC-bonded monovalent organic radicals.

The inventive RTC compositions preferably comprise fillers. Examples offillers are nonreinforcing fillers, i.e. fillers having a BET surfacearea of up to 50 m²/g, such as quartz, diatomaceous earth, calciumsilicate, zirconium silicate, zeolites, metal oxide powders such asoxides of aluminum, titanium, iron or zinc, or mixed oxides thereof,barium sulfate, calcium carbonate, gypsum, silicon nitride, siliconcarbide, boron nitride, glass and plastic powder, such aspolyacrylonitrile powder; reinforcing fillers, i.e. fillers having a BETsurface area of more than 50 m²/g, such as pyrogenic silica,precipitated silica, carbon black such as furnace black and acetyleneblack, and silicon-aluminum mixed oxides of large BET surface area;fibrous fillers such as asbestos and plastic fibers.

The fillers mentioned may be hydrophobicized, for example by thetreatment with organosilanes or -siloxanes or with stearic acid, or byetherification of hydroxyl groups to alkoxy groups. In the case of thesole use of reinforcing silica as a filler, transparent RTC compositionsmay be prepared.

The components used to prepare the inventive compositions may each beone type of such a component or else a mixture of at least two differenttypes of a particular component.

The inventive crosslinkable compositions are preferably those whichcomprise

-   -   (A) inventive organopolysiloxanes,    -   (B) crosslinkers having at least three organyloxy radicals,    -   (C) condensation catalysts and    -   (D) filler.

The inventive crosslinkable compositions are more preferably those whichcomprise

-   -   (A) inventive organopolysiloxanes,    -   (B) from 0.01 to 5 parts by weight, based on 100 parts by weight        of (A), of silanes having at least three alkoxy radicals and/or        partial hydrolyzates thereof,    -   (C) from 0.01 to 3 parts by weight, based on 100 parts by weight        of (A), of condensation catalysts and    -   (D) from 0.5 to 20 parts by weight, based on 100 parts by weight        of (A), of filler.

The inventive compositions may be prepared in any manner known hitherto,for example by simply mixing the individual components, in which caseinventive siloxane used as component (A) may be prepared in situ.

For the crosslinking of the inventive RTC compositions, the typicalwater content of air is sufficient. If desired, the crosslinking mayalso be carried out at temperatures higher or lower than roomtemperature, for example at from −5 to 10° C. or at from 30 to 50° C.The crosslinking is carried out preferably at a pressure of thesurrounding atmosphere, i.e. from about 900 to 1100 hPa.

The present invention provides moldings produced by crosslinking theinventive compositions.

The inventive compositions may be used for all purposes for whichcompositions crosslinkable at room temperature by condensation reactionhave also been used hitherto. They are thus suitable in an excellentmanner, for example, as sealing compositions for joints, includingvertical joints, and similar cavities, for example of buildings, landvehicles, watercraft and aircraft, or as adhesives or cementingcompositions, for example in window construction or in the production ofdisplay cases, and also for producing protective coatings or elastomericmoldings, and also for the insulation of electrical or electronicdevices. The inventive RTC compositions are especially suitable aslow-modulus sealing compositions for joints with possible highaccommodation of motion.

In the examples described below, all specifications of parts withpercentages, unless stated otherwise, are based on the weight. Inaddition, all viscosity data are based on a temperature of 20° C. Unlessstated otherwise, the examples below are carried out at a pressure onthe surrounding atmosphere, i.e. at about 1000 hPa, and roomtemperature, i.e. at about 20° C., or at a temperature which isestablished when the reactants are combined at room temperature withoutadditional heating or cooling.

Below, Cy stands for cyclohexyl radical.

EXAMPLE 1

500 parts by weight of a silanol-terminal dimethylpolysiloxane having aviscosity of 1000 mPa·s, 500 parts by weight of atrimethylsilyl-terminal dimethylpolysiloxane having a viscosity of 100mPa·s are mixed with 4 parts by weight of a silane of the formulaCyHN—CH₂—Si(CH₃)(OCH₂CH₃)₂ in a planetary mixer, and the viscosity η¹ isdetermined and reproduced in Table 1. This polymer mixture is admixedwith 2 parts by weight of cyclohexyl isocyanate, and, after 5 minutes,30 parts by weight of methyltrimethoxysilane and 0.15 part by weight ofzinc acetylacetonate are added for catalysis. The course of theviscosity is measured and reproduced in Table 1.

COMPARATIVE EXAMPLE 1

500 parts by weight of a silanol-terminal dimethylpolysiloxane having aviscosity of 1000 mPa·s, 500 parts by weight of atrimethylsilyl-terminal dimethylpolysiloxane having a viscosity of 100mPa·s are mixed with 4 parts by weight of a silane of the formula(CH₃CH₂)₂N—CH₂—Si(CH₃)(OCH₂CH₃)₂ in a planetary mixer, and the viscosityη¹ is determined and reproduced in Table 1. Afterward, 30 parts byweight of methyltrimethoxysilane and 0.15 part by weight of zincacetylacetonate are added for catalysis. The course of the viscosity ismeasured and reproduced in Table 1. TABLE 1 Viscosity in mPa · s Example1 Comparative example 1 η¹ 1312 560 η after 2 hours 992 480 η after 2days 960 200 η after 3 days 864 170

EXAMPLE 2

In a planetary mixer, 50.0 parts by weight of a silanol-terminaldimethylpolysiloxane having a viscosity of 80 000 mPa·s, 30.0 parts byweight of a trimethylsilyl-terminal dimethylpolysiloxane having aviscosity of 100 mPa·s are mixed with 0.1 part by weight of a silane ofthe formula CyHN—CH₂—Si(CH₃)(OCH₂CH₃)₂ and stirred for 5 minutes. Thispolymer mixture is admixed with 0.07 part by weight of cyclohexylisocyanate, and, after 5 minutes, 3.0 parts by weight ofmethyltrimethoxysilane and 0.015 part by weight of zinc acetylacetonateare added for catalysis. As soon as the silanol content is <30 ppm, asolid RTC preparation is compounded using 1.2 parts by weight of3-aminopropyltrimethoxysilane, 8.5 parts by weight of a pyrogenic silica(BET 150 m²/g) and 0.3 part by weight of a tin catalyst which isprepared by reacting di-n-butyltin diacetate and tetraethoxysilane. Thethus obtained composition is applied in a thickness of 2 mm to a PE filmand stored at 23° C./50% rel. atmospheric humidity. The skin formationtime is 15 minutes; the composition cures through within 24 hours andresults in an elastic vulcanized material.

COMPARATIVE EXAMPLE 2

In a planetary mixer, 50.0 parts by weight of a silanol-terminaldimethylpolysiloxane having a viscosity of 80 000 mPa·s, 30.0 parts byweight of a trimethylsilyl-terminal dimethylpolysiloxane having aviscosity of 100 mPa·s are mixed with 0.1 part by weight of a silane ofthe formula (CH₃CH₂)₂N—CH₂—Si(CH₃)(OCH₂CH₃)₂ and stirred for 5 minutes.Then, 3.0 parts by weight of methyltrimethoxysilane and 0.015 part byweight of zinc acetylacetonate are added. As soon as the silanol contentis <30 ppm, a solid RTC preparation is compounded using 1.2 parts byweight of 3-aminopropyltrimethoxysilane, 8.5 parts by weight of apyrogenic silica (BET 150 m²/g) and 0.3 part by weight of a tin catalystwhich is prepared by reacting di-n-butyltin diacetate andtetraethoxysilane. The composition is applied in a thickness of 2 mm toa PE film and stored at 23° C./50% rel. atmospheric humidity. The skinformation time is 15 minutes; however, the composition does not curethrough and does not give an elastic vulcanized material.

EXAMPLE 3

In a planetary mixer, 50.0 parts by weight of a silanol-terminaldimethylpolysiloxane having a viscosity of 80 000 mPa·s, 30.0 parts byweight of a trimethylsilyl-terminal dimethylpolysiloxane having aviscosity of 100 mPa·s are mixed with 0.1 part by weight of a silane ofthe formula CyHN—CH₂—Si(CH₃)(OCH₂CH₃)₂ and stirred for 5 minutes. Thispolymer mixture is admixed with 0.07 part by weight of cyclohexylisocyanate, and, after 5 minutes, 3.0 parts by weight ofethyltriacetoxysilane are added. 8.5 parts by weight of a pyrogenicsilica (BET 150 m²/g) and 0.01 part by weight of dibutyltin diacetateare used to compound a solid RTC preparation. The composition is appliedin a thickness of 2 mm to a PE film and stored at 23° C./50% rel.atmospheric humidity. The skin formation time is 10 minutes; thecomposition cures through within 24 hours and results in an elasticvulcanized material.

1-8. (canceled)
 9. An organopolysiloxane, comprising: at least one unitof the formulaR₂SiO_(2/2)  (I) at least one unit of the formula(R⁵O)R₂SiO_(1/2)  (II) and at least one unit of the formula(R¹R²N—CR¹⁰ ₂—)RSiO_(2/2)  (III) where R each is the same or differentand is a monovalent, optionally substituted hydrocarbon radical, R′, R³,R⁴, R⁷, R⁸ and R⁹ are each independently the same or different and areas defined for R, R¹and R¹⁰ are each independently the same or differentand are hydrogen or are as defined for R, R² independently is a—C(═O)—NH—R³ radical or a —C(═O)(OR⁴) radical, R⁵ each is the same ordifferent and is hydrogen or a —(R′₂Si—R⁶—)_(y)Si(OX)_(a)R⁷ _(3−a)radical, X is —C(═O)—R⁸, —N═CR⁹ ₂ or is as defined for the R radical, R⁶each is the same or different and is a divalent, optionally substitutedhydrocarbon radical, a is 1, 2 or 3, and y is 0 or
 1. 10. Theorganopolysiloxane of claim 9, comprising

where o is ≧1, m is ≧1 and n is ≧1, wherein the n and o moieties aredistributed in any manner within the molecule.
 11. Theorganopolysiloxane of claim 10, wherein the values for m, n and o areselected such that the viscosity of the organopolysiloxane is between5000 and 1,000,000 mPa·s at 20° C.
 12. A process for preparing anorganopolysiloxane of claim 9, comprising: a) reactinghydroxy-terminated organopolysiloxane(s) with silane(s) of the formulaR¹HN—CH₂—SiR(OR¹¹)₂  (V) and/or partial hydrolyzates thereof, where eachR¹¹ is the same or different and is as defined for R, b) convertingamino groups of the reaction product obtained in a) to urea groups orcarbamate groups by reacting with one or more compounds selected fromthe group consisting of isocyanates, reactive isocyanate derivatives,and reactive carboxylic acid derivatives, and, c) optionally,end-capping organopolysiloxane(s) obtained in b) with one or moresilanes of the formula Si(OX)_(a′)R⁷ _(4−a′) (VI) where a′ is 2, 3 or 4.13. The process of claim 12, wherein amino groups of the reactionproduct obtained in a) are converted in b) to urea groups by reactingwith isocyanate.
 14. A condensation crosslinkable composition,comprising at least one organopolysiloxane (A) of claim
 9. 15. Acondensation crosslinkable composition, comprising at least oneorganopolysiloxane (A) prepared by the process of claim
 12. 16. Thecrosslinkable composition of claim 14, further comprising (B) from 0.01to 5 parts by weight, based on 100 parts by weight of (A), of silane(s)having at least three alkoxy radicals and/or partial hydrolyzatesthereof, (C) from 0.01 to 3 parts by weight, based on 100 parts byweight of (A), of condensation catalyst(s) and (D) from 0.5 to 20 partsby weight, based on 100 parts by weight of (A), of filler(s).
 17. Amolding produced by crosslinking the composition of claim
 14. 18. Amolding produced by crosslinking the composition of claim
 15. 19. Acrosslinkable composition, comprising (A) at least oneorganopolysiloxane of claim 10, (B) from 0.01 to 5 parts by weight,based on 100 parts by weight of (A), of silane(s) having at least threealkoxy radicals and/or partial hydrolyzates thereof, (C) from 0.01 to 3parts by weight, based on 100 parts by weight of (A), of condensationcatalyst(s) and (D) from 0.5 to 20 parts by weight, based on 100 partsby weight of (A), of filler(s).